Compressed air audits let you find the leaks in your system

An easy first step in improving system efficiency in this type of system is to identify and eliminate any false demand in the system such as dormant processes that are still connected to the air system or infrequently used processes that constantly draw air.

By James Green and George Mankos, Ingersoll Rand

08/12/2010

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According to the U.S. Department of Energy, compressed air systems can account for as much as 30% of a plant’s total energy consumption. With ever-increasing pressures to reduce costs and maximize efficiency, these systems are often focal points for savings opportunities. Fortunately, such opportunities exist within every compressed air system

Air systems are commonly used for highly intermittent applications such as assembly or painting operations where air usage can swing significantly as down-stream users consume air in highly variable quantities. In this type of system, proper separator tank setup and right-sized air storage tanks are critical for improving process stability and reducing energy consumption.

Flow control valves can also be used to run different portions of the system at different pressures to maximize efficiency across varying operations. Using a variable speed compressor as a trim compressor will also help keep air flow constant and energy demands down.

At the other extreme are continuous duty applications that use air in a constant and stable manner. In this scenario, compressors should operate at peak performance at all times to maximize efficiency.

An easy first step in improving system efficiency in this type of system is to identify and eliminate any false demand in the system such as dormant processes that are still connected to the air system or infrequently used processes that constantly draw air. Utilizing system controllers can help balance the need for air between compressors and prevent compressors from wasting energy by running without generating air.

Questions and answers

Regardless of the system demand situation, the closer that supply can be matched with demand, the more efficient the air system will become. Answering the following basic questions can help determine how well matched supply and demand are in an air system:

· Is the air supply adequate?

· Is air being produced when it is needed and in the correct quantity?

· How efficiently is the compressed air system producing the air? Is it over or underutilized?

· Is the air of sufficient quality?

· Is the air delivered to the end use process at the correct pressure?

· How efficient is the distribution system in getting the air to the downstream users?

· Are there any bottlenecks in the system that cause pressure drops?

· Are there leaks in the system that could cause system degradation?

· How efficiently is the air used by the end user?

· Is air being wasted by end processes or tools?

· Are there dormant or old processes that no longer need to utilize the air supply?

· Is the air system’s performance adequately measured?

· How is system performance measured? What metrics are in place?

· Is the system measured and evaluated using those metrics on a regular basis?

· Who is accountable to ensure the system is performing at peak efficiency?

Audits deliver results

While the questions above provide a good starting point, extensive analysis is required to properly evaluate air system performance and identify a system-specific solution. To do this most effectively, consider having a professional system audit conducted. A professional air audit team can provide a comprehensive analysis of current system performance and use this information to create a detailed, site-specific improvement plan.

“An audit helps customers gain a strong understanding of how their air system works. It gives them the power to make improvements now and the knowledge they need to keep their system running at maximum efficiency for the future” said Chip Rhoden, regional auditor for Ingersoll Rand.

The Trane production facility in Pueblo, CO provides a perfect example of the potential benefits a professional air system audit can provide. As part of the plant’s focus on continuous improvement, Trane commissioned an air audit with the goal of identifying ways to reduce energy consumption and improve process capability by narrowing the pressure band to the down-stream equipment.

An Ingersoll Rand audit team began by interviewing key personnel and touring the facility to understand how the air system was being used. Next, they meticulously mapped the supply and distribution of the existing system within the plant. The supply was calculated along with all of the storage capacity and down-stream consumption by all processes. Then, the team installed measurement and recording systems to measure customer use and gather baseline data for evaluation. Finally, the team measured the system for leaks using ultrasonic leak detection equipment to eliminate false demand.

Making the changes

As often found in older systems, the audit identified that much of the compressed air equipment that had been installed as the facility added capacity was not as efficient as it could be. There were two separate air systems at opposite ends of the building that functioned independently of each other. Additionally, the air storage within the system was inadequate for some of the processes they supported, which led to inefficiency and caused quality control issues during production. Finally, redundant compressors were running and consuming excess energy.

Armed with the data and recommendations from the air audit, Trane combined the two separate compressed air systems into one, added flow controllers, added an energy management system and implemented a leak mitigation plan to maintain system efficiency.

“We will save up to 40% of our air system energy costs and up to 10% of our total electrical power bill as a result of this air system audit. The air systems team was exceptional in their knowledge and very easy to work with. I wish we could come out of every survey with this scope of achievable savings,” said Jim Meyer, maintenance and facilities manager for the Trane operations in Pueblo.

By gaining an understanding of how air systems work, answering some questions about the air system’s use and performing basic analysis, air systems can be optimized to run at maximum efficiency and help reduce a plant’s overall energy costs.

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